Reverse Osmosis Usage Check

[Bradders]

Hi All,

In terms of RO water, and moving your hard tap water to a softer one, is is really just a case of mixing tap water with RO water to create the softer water?

Just wanted to check this out before I think about trying anything on my Hard (nearly Very Hard) tap water in an established aquarium. I know pure RO is dangerous to fish, and also not sure why some mix with tap and some use a remin product instead.

Any thoughts and things to watch for would be great

Thanks,
Brad

 

[John q]

Ah, but it all depends on what the TDS is made up of, though, right?!

Obviously 🫣

 

[fredi]

Well, that will obviously be a bad thing. Not because of the TDS level but due to what the TDS is made up of... Those compounds especially the NH4 and Cu are highly toxic (lethal) at those levels. When we discuss TDS we obviously shouldn't dispense with common sense... It matters what the TDS is made up of... No one ever said otherwise.

100% agree 👍

 

[Bradders]

🤣

 

[MichaelJ]

Cheers,
Michael

 

[Bradders]

 

[MichaelJ]

This thread has been excellent for engagement. I am learning a lot about this topic on the way.

Thank you. Yeah, John and I love a good banter.

I wonder what will happen to the plants!?

Plant cells rely on osmosis (and turgor pressure) as well for water and nutrient exchange, but what the difference in osmotic pressure imposed by waters that have say a TDS of 400 ppm vs. 200 ppm (assuming otherwise healthy non-toxic nutrient and mineral levels), I can't tell. My suspicion though, is when we talk about picky soft water plants that besides requiring low alkalinity (low KH), the sensitivity to suboptimal osmotic pressure may play a larger role (even if minor compared to alkalinity/pH) with those species vs other hardier plant species. I don't know.🤷‍♂️

Lol, it's been scientifically proven that aquatic plants shrivel up and die at Tds levels bellow 250ppm 😁

haha, yes. And that explains why none of your plants are growing at 140 ppm

Cheers,
Michael

 

[John q]

Thank you. Yeah, John and I love a good banter.

I think!! That's what makes this forum tick?

haha, yes. And that explains why none of your plants are growing at 140 ppm

Purley for experimental reasons, but yes I shall be going lower in the not to distant.

 

[MichaelJ]

I think!! That's what makes this forum tick?

Sure thing!

Purley for experimental reasons, but yes I shall be going lower in the not to distant.

How low do you think you can go? ... In the tank where I keep the mineral content to a minimum (no invertebrates) and with very lean dosing I never managed to get much below 65-70 ppm (130-140 uS/cm)... ~2.5 dGH, 1.25 ppm N, 0.1 ppm P, 1 ppm K, 0.06 ppm Fe from Tropica Specialized every two weeks.... (On a side note: adding 14 ml of TS to 150 L actually adds 10 ppm to my TDS, so there is more there than just the NPK and macros ... probably sulphates and stabilizers).

Cheers,
Michael

 

[Bradders]

How low do you think you can go? ... In the tank where I keep the mineral content to a minimum (no invertebrates) and with very lean dosing I never managed to get much below 65-70 ppm (130-140 uS/cm)... ~2.5 dGH, 1.25 ppm N, 0.1 ppm P, 1 ppm K, 0.06 ppm Fe from Tropica Specialized every two weeks.... (On a side note: adding 14 ml of TS to 150 L actually adds 10 ppm to my TDS, so there is more there than just the NPK and macros ... probably sulphates and stabilizers).

Purley for experimental reasons, but yes I shall be going lower in the not to distant.

Isn't there a point where if you go too low, its not great for the fish?

 

[Wookii]

Isn't there a point where if you go too low, its not great for the fish?

Depends on the fish. In blackwater habitats conductivity can drop below 20us (about 13ppm TDS), but that might not be practical in an aquarium as the pH could drop too low for the microbial community. I think about 40-50ppm (60-80us) would probably be the lowest I'd attempt to go, though there'd be no shrimp in there and plants wouldn't be the focus.

@Conort2 keeps blackwater fish, and may be able to advise how low he has taken his tanks for breeding purposes etc

 

[dw1305]

Hi all,

In blackwater habitats conductivity can drop below 20us (about 13ppm TDS), but that might not be practical in an aquarium as the pH could drop too low for the microbial community.

I'm guessing that there will still be <"microbial nitrification occurring">, just at a lower rate than "normal". My guess would actually be that there aren't any naturally occurring aquatic environments where <"microbial nitrification doesn't occur">.

....... I was pretty sure the traditional view of cycling wasn't right, mainly because <"fixed nitrogen"> is a scarce and valuable resource in the natural environment, so it didn't make any ecological sense that the organisms that could utilise it were restricted to a few bacteria, with highly specialised requirements for growth.

An analogy would be that there is a big pile of money in the street, with a note saying "take me", but it is only ever picked up by a one-legged ginger Irish-man on a Thursday..........

I've found a paper. It isn't really my field, but it looks pretty useful, I'll add in @Andy Pierce as he may be able to give a more nuanced view.

Ni G, Leung PM, Daebeler A, Guo J, Hu S, Cook P, Nicol GW, Daims H, Greening C (2023). "Nitrification in acidic and alkaline environments". Essays Biochem. 11:67(4) pp. 753-768 <"Nitrification in acidic and alkaline environments">.

I think one of the issues with keeping blackwater fish (away from acidic, tannin and humic acid rich water), is that there is a lot more microbial activity in more "normal" water and this often leads to bacterial diseases and early mortality.

As an analogy I think it a bit like a person (let's just say an American) normally drinking heavily chlorinated water and regularly taking antibiotics and then going on holiday to "Mexico" and drinking the local water untreated.

Their decimated intestinal microbial biome isn't going to be in any condition to resist a new suite of (potentially opportunistically pathogenic) organisms and it is the same for blackwater fish when you take them out of their natural habitat and place them in "normal" water.

cheers Darrel

 

[Wookii]

My guess would actually be that there aren't any naturally occurring aquatic environments where microbial nitrification doesn't occur.

I was referring to an aquarium though Darrel. If we push the pH in a tank down to 4.5pH with a half decent fish load - especially is a lightly planted biotope tank, do we not risk ammonia build up from due to the low pH affecting the microbial community?

 

[dw1305]

Hi all,

If we push the pH in a tank down to 4.5pH with a half decent fish load ........ do we not risk ammonia build up from due to the low pH affecting the microbial community?

I think you probably would get issues. I think both microbial ammonia oxidation and the conversion of nitrite (NO2-) to nitrate (NO3-) would be compromised.

Have a look at <"Joe's tank">, that has a reasonable fish load, personally my version of "over-stocked" is if you can <"actually see any fish at all">.

I'm pretty sure that <"this wouldn't work">.

From <"Stocking of an Aquarium">

Some people would argue that all the total ammoniacal nitrogen (N) TAN would be in the form of ammonium (NH4+) and therefore much less toxic, but I think that <"is a slippery slope">.

....... - especially is a lightly planted biotope tank,

I would want a lot of floating, or emergent, plants to deal with fixed nitrogen, Water Lettuce (Pistia stratiotes) would probably be my weapon of choice and is <"biotope appropriate">.

This is a stream near Leticia, Columbia. <"Rio Orinoco biotope questions">.

cheers Darrel

 

[Bradders]

View attachment 216121

Plenty more space for fish there, @dw1305.

 

[Conort2]

@Conort2 keeps blackwater fish, and may be able to advise how low he has taken his tanks for breeding purposes etc

I’ve gone down as low as about 30-40 tds when I was initially trying to spawn my apistogramma lineata. Turns out that wasn’t needed at all and they successfully spawned in water with a tds around 120 or so.

I keep my black water fish at a tds of around 70-100. I think my tucano tetras would probably prefer it a fair bit lower but they seem to be doing fine.

 

[MichaelJ]

Isn't there a point where if you go too low, its not great for the fish?

Sure you need some minerals in there, not much for super soft water fish though. However, for fish adapted to very/moderately soft water kept in a planted aquarium we would never hit any lower bound... And the reason for that is we all provide some minerals in the from of Calcium, Magnesium, NPK and micros to support our plants. Even the leanest lean dosers amongst us wont get below the 15-30 ppm (30-60 uS/cm) range. If you look at the chart I posted in #25 you can see that many of those natural soft water way are even quite a bit below that level.

If we push the pH in a tank down to 4.5pH with a half decent fish load - especially is a lightly planted biotope tank, do we not risk ammonia build up from due to the low pH affecting the microbial community?

I think you're right, however at very low pH level toxic free ammonia would be virtually absent. Some Cardinal habitats in Rio Negro with a pH down in the pH of ~3-4 range would also have TAN levels in the upper/mid 20 mg/L supposedly due to limited microbial activity... sky high, but the actual toxic free ammonia at that pH level is a mere 0.00005 mg/L.

As an analogy I think it a bit like a person (let's just say an American) normally drinking heavily chlorinated water and regularly taking antibiotics and then going on holiday to "Mexico" and drinking the local water untreated.

I never heard of any Americans drinking water in Mexico... we drink Tequila... and lots of it... yes, we still get sick, so I guess the Tequila must be untreated



Cheers,
Michael

 

[hypnogogia]

I never heard of any Americans drinking water in Mexico

I never drink water because fish pee in it.

 

[John q]

How low do you think you can go?

It's more a case of what I think the levels should be knowing what I add in on a weekly basis.

Salts wise my current regime of Ca, Mg (Inc sulphate) and all the other ferts added, even after a few weeks of accumulation should add around 46ppm Tds. Tap water is fairly consistent at 55ppm, so assuming nothing added gets used that gives me a total of around 101ppm.
For sure waste products coming from the fish and plants will add to these numbers (lets guess 10~15ppm?) but conductivity throughout the week remains within 1~2 ppm and week in week out tds readings remain incredibly stable, so I'm kind of perplexed as to why we are now at 140ppm.

My current theory, aka "rabbit hole" revolves around the notion that my tanks are now approaching 3½ years old and something unknown to me has built up over this time and isn't being removed by the weekly 50% Wc.
Obviously I could of course be barking mad.

The plan is do a couple of back to back large water changes, vacuum some of the substrate and see where that leaves us. I suspect after doing this tds levels will end up leveling out at around 120ppm.

As an aside @Bradders despite my earlier comments about conductivity/tds numbers I think they are a fantastic bit of kit for monitoring trends in our tanks. 😀

 

[MichaelJ]

I never drink water because fish pee in it.

Ha... WC Fields...

Cheers,
Michael

 

[hypnogogia]

Ha... WC Fields...

Cheers,
Michael

I wasn’t quite sure who’d said it originally. I thought it might have been Ernest Hemingway, but WC Fields it is.